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Radiologists and physicians need to be aware of potential harms associated with access to patient radiation exposure histories, according to a commentary in the June issue of Radiology. With access to previous histories, physicians might fall prey to the fallacy that they can reduce the risks of previous exposure by bypassing current CT exams. Such false logic might lead to more harm than good, cautioned the authors.

The drive to develop and implement systems to track patient radiation history has gathered momentum. “Although it is obvious that patient dose histories could provide valuable information that would help avoid duplicate—and therefore unnecessary—CT examinations, physicians must also be careful not to misuse imaging histories in clinical decision making,” wrote Jonathan D. Eisenberg, BA, from the Institute for Technology Assessment and department of radiology at Massachusetts General Hospital in Boston, and colleagues.

Eisenberg et al focused on the pitfalls of sunk cost bias, a financial term that refers to irrecoverable costs. Sunk costs cannot be recouped, and therefore, should not influence current decision making.

In the case of radiation exposure, a patient’s previous radiation history should not factor into the decision to order a current exam, according to Eisenberg and colleagues.

The researchers offered the example of two similar hypothetical patients who present with symptoms of possible appendicitis. One has no previous exposure to radiation; the second has undergone 20 CT studies for surveillance of a treated and cured cancer and has a cumulative exposure of 180 mSv.

According to the linear no-threshold model, each dose exposure has an independent effect on a patient’s cancer risk. The harms and benefits of the current CT to evaluate for appendicitis would be identical for the two patients, according to the model. That is, past radiation exposure should not influence the decision to perform the CT exam.

“A decision against an additional CT examination will not reduce the cancer risks—sunk costs—incurred with previous examinations,” wrote Eisenberg and colleagues.

The researchers concluded by emphasizing the need for education and wrote that the radiology community should play a leadership role in communicating the concepts of the linear no-threshold model and the sunk cost bias. “If we fail to prioritize related educational efforts, we all risk succumbing to sunk cost biases and our well-intentioned decisions to spare patients additional diagnostic radiation may ultimately cause more harm than good.”